[unreadable] Quantitative physiologic modeling often requires an accurate radioactivity input function characterized by continuous data acquisition. Positron Emission Tomography (PET) is a powerful imaging technique for studies designed to non-invasively quantify physiologic processes in vivo. By combining PET with an accurate input function, unique kinetic parameters can be obtained and used in combination with appropriate mathematical models to obtain glucose metabolic rates in a variety of organs under normal and/or pathologic conditions. These data are useful in the diagnosis and characterization of diseases and their response to a given course of pharmacologic or behavioral therapy. Unfortunately, the invasive withdrawal of these samples represents discomfort for the patient and a potential health risk for hospital personnel. Therefore, the goal of this proposal is to design and construct a novel wrist detector that will be used to quantitatively and non-invasively measure arterial radioactivity. This wrist detector has several advantages over direct invasive blood withdrawal techniques which include the reduction of pain, the reduction of risks associated with blood borne pathogens and radiation exposure, and the elimination of the radioactivity dispersion which results from blood removal itself. The scientific and technical challenges of this wrist detector include issues related to sensitivity, the background associated with the venous blood pool and nearby tissue radioactivity, random coincidences from the rest of the body and scattered photons from nearby bone. In addition, it is important to increase the temporal resolution for radioactivity assessment in order to obtain the most accurate input function possible for diagnostic evaluation. Specifically, we propose to address each of these issues in the fabrication of a novel prototype wrist detector that can be used to measure arterial radioactivity concentrations with sufficient sensitivity and temporal resolution to be useful for kinetic modeling. Preliminary studies in our laboratory including the LSO/APD platform coupled with the ASIC development have shown that this is approach and design are feasible. Upon successful completion of our proposed studies, we will non-invasively generate an arterial input function that greatly reduces biohazards associated with blood withdrawal as well as the discomfort associated with arterial cannulation. [unreadable] [unreadable]